This invention relates to an apparatus and method for inserting, and removing, a flexible first material into a second material. In particular, the invention relates to an apparatus and method for installation and extraction of pipelines in boreholes. Even more particularly, the invention relates to an apparatus and method for installation and extraction of pipelines in horizontally directionally drilled boreholes.
Many forces come into play whenever it is necessary for one material to be inserted into another material. In the case where a flexible first material is inserted into a second material, one of the major forces that must be accounted for is buckling load. As is known in the art, the xe2x80x9cEulerxe2x80x9d buckling load for simple column buckling is determined from the relationship between material modulus of elasticity (E), moment of inertia (I) for the column, and the square of the column length (L). Buckling load, therefore, is proportional to: (E)(I)L2. The stiffness and/or flexibility of the first material is a determinant of the strength of it under axial compression. If more buckling load is encountered than the xe2x80x9cstiffnessxe2x80x9d of the flexible first material can accommodate, the flexible first material will be distorted, or fail, or both.
By way of background, an example from the field of installing and removing pipelines in horizontally directionally drilled boreholes is provided. A variety of techniques have been developed for creating horizontally directionally drilled boreholes. One technique is described as a xe2x80x9ccontinuous wellxe2x80x9d where the borehole enters the ground at one point, traverses underground for some distance and then exits the ground at a second point. Another technique is described as a xe2x80x9cblind wellxe2x80x9d where the borehole enters the ground at one point traverses underground for some distance and then stops. In some cases, the borehole enters the ground at one point, traverses underground for some distance and then exits from the ground into another medium such as water.
No matter the technique that is used, drilling the borehole is necessarily followed by the requirement of placing a pipe in the borehole. Immediately, the problems of axial compression loads and buckling limits are encountered. One prior art attempt to overcome these problems is to pull on the leading end of the pipe at the same time it is being pushed into the borehole. This procedure, however, requires pulling equipment to be established at the exit of the borehole, adding cost to the procedure. In some cases, however, there may be no room at the exit of the borehole for setting up the pulling equipment. Obviously, in other cases, such as with a blind well, there is simply no way that a pulling force may be applied to the leading end of the pipe. The most common procedure for completion of a continuous well in a borehole is to assemble the pipe on the exit side, space permitting, and to pull the pipe back to the entry hole by means of the drillpipe.
Other factors contribute to the difficulties of placing a pipe in the borehole. One factor concerns how the pipe is constructed. In the prior art, long sections of pipe, plastic and metal, are created by the use of screw joints. By way of example, in order to create a one thousand foot length of HDPE plastic pipe from fifty sections twenty feet long, it is first necessary to weld one male and one female end to two separate sections of pipe. For one thousand feet of pipe, these two welds for each section, one for each end, typically take two days to create and cost approximately $220.00 each or a total of $11,000.00. Additionally, the male/female joint has an outside diameter in most cases that is larger than the outside diameter of the section of pipe between the joint. In the normal case, then, additional borehole reaming is required in order to accommodate the increased diameter of the joints. A representative amount of time added by this requirement for additional borehole reaming is ten days rig time or one hundred and twenty hours. Also, in a pipe line installation of this kind, a typical pipe line installation time is sixteen hours of rig time. This time includes, among other things, the time it takes to join each joint prior to insertion into the borehole.
This time-consuming and costly procedure which is now the current state-of-the-art is further limited by the fact that the pipe line is only as strong as its weakest point which happens to be at the point of the multiple male and female joints. Failure of the pipe, breaking completely or partially, and/or leaking at the joints, is commonplace particularly when the material, ground, into which the pipe is inserted, resists insertion of the pipe. That is to say, in most cases, the friction encountered during insertion of pipe in the ground generates significant axial compression loads which cause deflection and/or failure of the pipe. These problems exist with thin wall metal pipelines, well screens and any other long thin cylinders placed in directionally drilled boreholes.
Thus, there is a need in the art for providing an apparatus and method for inserting, and removing, a flexible first material into a second material that overcomes the deficiencies found in the prior art. It, therefore, is an object of this invention to provide an apparatus and method for inserting, and removing, a flexible first material into a second material that is easy to use and inexpensive; that decreases the time required for inserting and/or removing the flexible first material; that enables the use of existing drilling machinery; and which does not require the leading end of the flexible first material to be pulled.
Accordingly, the apparatus for inserting, and removing, a flexible first material into a second material includes a movable carriage. An adjustable clamp is connected to the movable carriage and is adjustable between an open position and a clamped position on the flexible first material. In a preferred embodiment, in cases where the resisting friction forces are high or the buckling strength of the flexible first material is low, a receiver stiffener casing is configured to receive and support the flexible first material as the flexible first material is inserted into and removed from the second material.
In a preferred embodiment, in a slant drill rig with a stationary track and a movable drill for drilling a borehole in the ground, a push-pull apparatus for inserting and removing cylindrical tubing in the borehole includes a carriage attached to the movable drill. An adjustable clamp is connected to the carriage, adjustable between an open position and a clamped position on the cylindrical tubing. In a preferred embodiment, in cases where the resisting friction forces are high or the buckling strength of the flexible first material is low, a receiver stiffener casing is configured to receive and support the cylindrical tubing as the cylindrical tubing is inserted into and removed from the borehole. In a further preferred embodiment, the adjustable clamp includes two halves conformed to the dimensions of the exterior of the cylindrical tubing. In another preferred embodiment, the adjustable clamp is hydraulically operable and provides progressive grip pressure in the clamped position. In other preferred embodiments the two halves are split horizontally and are separated by a longitudinal gap when in the clamped position.
In a still further preferred embodiment, an axial tilt device is connected to the adjustable clamp. In another preferred embodiment, the receiver stiffener casing is connected to the slant drill rig by means of a drill rig connection. Other preferred embodiments of the apparatus of the present invention are disclosed more fully hereafter.
A method for inserting a flexible first material into a second material includes the steps of providing a movable carriage and attaching an adjustable clamp to the movable carriage so that the adjustable clamp is adjustable between an open position and a clamped position on the flexible first material. In a preferred embodiment, in cases where the resisting friction forces are high or the buckling strength of the flexible first material is low, a casing is provided and configured to receive and support the flexible first material as the flexible first material is inserted into the second material. The flexible first material is placed within the adjustable clamp and the adjustable clamp is placed in the clamped position. At that point, the movable carriage is moved so as to pass a leading end of the flexible first material into the second material beginning with the leading end. In a further preferred embodiment of the method, the adjustable clamp is placed in the open position and the movable carriage is moved away from the leading end. The adjustable clamp is then placed in the clamped position and the movable carriage is moved toward the leading end. These steps are repeated continuously until a desired amount of flexible first material has been inserted into the second material. Other preferred embodiments of the method of the present invention, including the preferred embodiment of the method for removing the flexible first material from the second material, are discussed and disclosed more fully hereafter.